Remove conditionals for MPI version 2, it is always true

It was removed 9 years ago.

dune/istl/owneroverlapcopy.hh

@@ -659,15 +659,13 @@ namespace Dune {
       if (freecomm==true)
         if(comm!=MPI_COMM_NULL)
         {
-#ifdef MPI_2
           // If it is possible to query whether MPI_Finalize
           // was called, only free the communicator before
           // calling MPI_Finalize.
           int wasFinalized = 0;
           MPI_Finalized( &wasFinalized );
           if(!wasFinalized)
-#endif
-          MPI_Comm_free(&comm);
+            MPI_Comm_free(&comm);
         }
     }